Patent GB-202270-A (GB)
Title: Improvements in or relating to variable pitch propellers
IPC: B64C11/36
Filed: 1923-02-07
Abstract: 202,270. Heath, S. Aug. 9, 1922, [Convention date]. Screw and like propellers.-A variable-pitch screw propeller has means for adjusting the blades while running, for automatically stopping the adjustment after a predetermined limit, for indicating the pitch of the blades, and for varying the amount of power supplied to the propeller. The blades 13, Fig. 1, are secured in ferrules 14 rotatably mounted in the sockets of the hub 10, and having internal gears 15 on their ends, meshing with pinions 16, 17 connected by gears 20, 21 to a worm shaft 24. A gear-wheel 25 on each worm shaft meshes with a pinion 26 secured to a double gear 27 journaled on the hub. One part of each gear 27 meshes with a gear 28, and a gear 29 concentric with the gear 28 meshes with two pinions 30 journaled on the hub and meshing with the gears 27. The gear 29 is secured to a brake drum 33 and the gear 28 to a brake drum 35, and they are mounted on a tubular extension 32 of the hub. Rotation of the blades is caused by a relative rotation of the brake drums, which normally rotate with the propeller and at the same speed, due to the application of one of the brake shoes 41, Fig. 3, to one of the drums. The shoes and drums are housed in a casing 40, and are normally kept apart by springs 44. Rocking arms 46, Fig. 3, pivoted to rods 48 at one end, have lugs 47 at the other end, the lugs on each arm can engage with either one of two adjacent brake shoes. The rods 48 are connected to a yoke 50, lugs 53 on which engage with shoulders 52 on a manuallyoperated rod 51 controlled by a spring 57. The mechanism for automatically stopping rotation of the blade is as follows :-A gear 60 secured to the drum 33 and a gear 61 secured to the drum 35 mesh respectively with gears 62, 63, Fig. 3, which drive worm shafts 65, 68. Worms 66, 69 operate a differential gear mechanism, Fig. 7, comprising worm-wheels 72, 73 loosely mounted on a shaft 74, and bevel gears 77, 78 integral with the worm-wheels engaging bevel gears 76 on a spider 75 secured to the shaft 74, which is normally stationary but will rotate with the blades owing to the relative rotation of the brake drums, and is arranged to have twice the angular displacement of the blades. Cams 80, 81 on the shaft 74 operate a forked cam lever secured to a rocking shaft 83, Fig. 8, by a pin 87 which can be inserted in a hole 100 in the shaft 83, when it is desired that the blades shall not be limited in their angular adjustment. Arms 90 on the shaft 83 are connected by links 91 to rods 92 engaging the yoke 50. The raising or lowering of the yoke due to the action of the cams disengages or engages the lugs 53 on the yoke from or with the shoulders 52 on the rod 51. An indicator showing the, angular position of the blades is driven by a bevel gear 95 on the shaft 74. To control the supply of motive fluid to the motor, a forked rock lever 105 is operated by cams 103, 104 on the shaft 74, and is secured to a rock shaft 108 having an arm 109 comprising two parallel members yieldingly held in position by two spring members 110. A rod 111 connects the arm to the throttle valve of the motor. The cam 103, Fig. 14, has a part 103<a> to close the valve at the point of zero pitch, and the cam 104 has an indentation 104<a> to open the valve after the point has been passed. Manual rotation of the blades is effected by a shaft 112 having a gear 113, Figs. 1 and 3, which may be drawn into engagement with the gear 63.